Polycrystalline diamond (PCD) materials and PCD elements formed therefrom are well known in the art. Conventionally, PCD is formed by combining diamond grains with a suitable binder/catalyst material. The mixture is subjected to conditions of extremely high temperature/high pressure, where the binder/catalyst material promotes desired intercrystalline diamond-to-diamond bonding between the grains, thereby forming a polycrystalline diamond structure. The resulting PCD structure produces enhanced properties of wear resistance and hardness, making PCD materials extremely useful in aggressive wear and cutting applications where high levels of wear resistance and hardness are desired.
Binder/catalyst materials that are typically used for forming PCD include Group VIII elements, cobalt (Co) being the most common. Conventional PCD can comprise from 85 to 95% by volume diamond and a remaining amount of the binder/catalyst material. The binder/catalyst material is present in the PCD material within interstices that exist between the bonded together diamond grains.
One problem known to exist with such conventional PCD materials is thermal degradation due to differential thermal expansion between the interstitial cobalt binder/catalyst material and the intercrystalline bonded diamond. This is known to occur at temperatures of about 400° C. Upon sufficient expansion, the diamond-to-diamond bonding may be ruptured and cracks and chips may occur.
Another problem known to exist with convention PCD materials involves the presence of the binder/catalyst material in the interstitial regions adhering to the diamond crystals, and another form of thermal degradation. This presence of the binder/catalyst material is known to catalyze phase transformations in diamond (converting to carbon monoxide, carbon dioxide, or graphite) with increasing temperature, thereby limiting practical use of the PCD material to about 750° C.
Attempts at addressing this issue are known in the art. Generally, these attempts have involved the formation of a PCD material having an improved degree of thermal stability when compared to the conventional PCD material discussed above. One known technique of producing a thermally stable PCD material involves a multi-step process of first forming a conventional sintered PCD element, i.e., one formed by combining diamond grains and a cobalt binder/catalyst material at high temperature/high pressure, and secondly selectively removing the binder/catalyst material from a working surface of the sintered element.
While this multi-step process results in the removal of the binder/catalyst from a select portion of the PCD element working surface, and is promoted as providing improved thermal stability in the region of the element where the binder/catalyst has been removed, it involves a multi-step process that is both time consuming and labor intensive.
It is, therefore, desired that a PCD material be developed that has improved thermal stability when compared to conventional PCD materials. It is also desired that such PCD material be capable of being prepared during a single manufacturing process.